Internal combustion engines ("ICEs") are generally classified as either constant volume or constant pressure. Otto cycle engines operate by exploding volatile fuel in a constant volume of compressed air near top dead center while diesel cycle engines burn fuel in a modified cycle, the burning being approximately characterized as constant pressure.
External combustion engines ("ECEs") are exemplified by steam engines and turbines and some forms of gas turbines. It has been known to supply a gas turbine with a fluid heated and compressed from an external fluid supply source and to operate various motor devices from energy stored in this compressed gas.
It is also known to burn fuel in a chamber and exhaust the combustion products into a working cylinder, sometimes with the injection of water in accordance with the rising temperature. These may also be classified as ECEs.
Some other devices have been proposed in which combustion chambers are cooled by addition of water internally rather than employing external cooling. Still another form of apparatus has been proposed for operation on fuel injected into a combustion cylinder as the temperature falls, having means to terminate fuel injection when the pressure reaches a desired value.
Each of these prior engines has encountered difficulties which have prevented their general adoption as a power source for the operation of prime movers. Among these difficulties have been the inability of such an engine to meet sudden demand and/or to maintain a constant working temperature or pressure as may be required for efficient operation of such an engine.
Furthermore, control of such engines has been inefficient, and the ability of the gas generator to maintain itself in standby condition has been wholly inadequate. In all practically applied engine configurations the requirement for cooling the confining walls of the work cylinders has resulted in loss of efficiency and a number of other disadvantages previously inherent in ICEs.
The present invention overcomes the limitations of the prior art described above. First, the requirement of air or liquid external cooling is eliminated by injecting water into the combustion process to control the temperature of the resulting working fluid. When water is injected and converted into steam in this way, it becomes a portion of the working fluid itself, thus increasing the volume of working fluid without mechanical compression. The working fluid is increased when excess combustion gas temperature is transformed into steam pressure.
In the present invention, independent control of the combustion flame temperature and fuel to air ratio is used in order to accommodate the requirements of a working engine. Control of the flame temperature also prevents the formation of NO.sub.x and the disassociation of CO.sub.2 as described below.
The present invention also utilizes high pressure ratios as a way of increasing efficiency and horsepower while simultaneously lowering specific fuel consumption ("sfc"). When water is injected and converted into steam in the combustion chamber of the present invention, it acquires the pressure of the combustion chamber. It should be noted that this pressure of the combustion chamber is acquired by the steam irrespective of the pressure ratio of the engine. Thus, a higher pressure ratio can be obtained in the engine without expending additional work for performing compression for new steam or water injection. Because of massive water injection used in the present invention, there is no need to compress dilation air typically used in prior art systems for cooling. The elimination of this requirement results in an enormous energy savings to the system.
Because the pressure ratio is increased in a device using water injection as taught in the present invention, several advantages are apparent. To begin with, no additional work is required to compress water or steam further after they have been initially compressed; in other words, after compressing steam to 2 atmospheres, no additional work is required to compress it further to a higher pressure. This is unlike air, for example, for which additional work must be expended to raise it to higher pressures and thus acquire additional working fluid mass. Furthermore, when water is injected and converted to steam in the present invention, it acquires the pressure of the combustion chamber without additional work. This steam also has constant entropy.
In the present invention excess waste heat from combustion is converted to steam pressure and as an additional mass for the working fluid without mechanical compression. In contrast, in a typical Brayton Cycle Turbine, 75% of the mechanically compressed air is used for air dilution with the products of combustion in order to reduce the temperature of the working fluid to Turbine Inlet Temperature ("TIT") requirements.
Since the steam doubles or more the working fluid and produces 25% or more of the net horsepower, the water can be seen to serve as a fuel in this new thermodynamic system because it supplies pressure, power and efficiency to the present system.
The cycle of the present invention may be open or closed with respect to either or both air and water. Desalination or water purification could be a byproduct of electric power generation from a stationary installation, where the cycle is open as to air but closed as to the desalinated water recovery. Marine power plants or irrigation water clean up systems are also viable environments.
The present cycle can also be employed in the closed cycle phase in mobile environments, e.g. autos, trucks, buses, commuter aircraft, general aviation and the like.